For therapy of a blood vessels of the head and neck, for example, a treatment catheter (treatment device) inserted into the blood vessel is used. Since the treatment catheter is generally small in diameter, a pushing force (pushability) and torque (for rotation) applied to the catheter from the proximal side are difficult to transmit to the distal side, due to buckling or bending.
In view of this, prior to insertion of the treatment catheter, a guiding catheter is inserted into the carotid artery communicating with a blood vessel of the head or neck where the region to be cured exists. A distal portion of the guiding catheter is engaged with the carotid artery, and the guiding catheter is fixed to be immovable at the position (target site). This fixation is called engagement.
After the guiding catheter is thus engaged, a guide wire and the treatment catheter are inserted into the guiding catheter, the treatment catheter is moved to protrude from the distal end of the guiding catheter, and is inserted into the blood vessel of the head or neck.
Here, since the blood vessel and the carotid artery are weaker to external forces than cardiac blood vessels and are very susceptible to damage, it is desirable for a distal portion of the guiding catheter to be more flexible. When the distal portion of the guiding catheter is insufficient in flexibility, it may injure the blood vessel. Known guiding catheters having distal portions exhibiting desirable flexibility attributes nevertheless are susceptible of shortcomings.
When a proximal portion of the guiding catheter is pushed in the distal direction to thereby move the guiding catheter in the distal direction, its distal portion is likely to be deflected so that the moving distance of the distal portion is shorter than the pushing-in distance of the proximal portion, and the steerability is poor accordingly.
At the time of inserting or drawing the treatment catheter into or out of the indwelling guiding catheter, the distal portion of the guiding catheter may be disengaged from the carotid artery, and the guiding catheter may slip off from the target site.
Meanwhile, catheter assemblies which each include an outer catheter having an outer catheter body and an outer catheter hub and an inner catheter having an inner catheter body capable of being inserted in the outer catheter body and an inner catheter hub are disclosed in International Application Publication No. WO 2005/056100 (hereinafter referred to as Patent Document 1), Japanese Patent Laid-Open No. 2005-553 (hereinafter referred to as Patent Document 2), and Japanese Patent Laid-Open No. 2004-357805 (hereinafter referred to as Patent Document 3). These catheter assemblies are mainly (cardiac) catheter bodies adapted to be inserted in a cardiac blood vessel. Each of the catheter assemblies is inserted into the blood vessel in an assembled condition in which the inner catheter is coupled to (fitted in) the outer catheter (the condition will hereinafter be referred to simply as “the assembled condition”).
In the catheter assembly described in Patent Document 1, however, in the assembled condition a distal portion of the inner catheter only protrudes slightly from the distal end of the outer catheter, so that the inner catheter has only the function of preventing damage to the blood vessel from occurring.
In addition, since the inner catheter body does not have any reinforcing material layer, it is poor in steerability. For example, it is difficult to change the direction of the inner catheter by operating the inner catheter alone.
The inner catheter of the catheter assembly described in Patent Document 2 includes a reinforcing material layer which is provided to extend to the distal end of the inner catheter body, and, therefore, the distal portion is insufficient in flexibility.
Further, in the catheter assembly described in Patent Document 3, a distal portion of the inner catheter is higher in rigidity than a distal portion of the outer catheter, and does not protrude from the distal end of the outer catheter (the distal ends of the inner and outer catheters coincide with each other). Therefore, the distal portion of the inner catheter has a poor inhibitive effect on damage to blood vessels.
In addition, since the inner catheter body does not have any reinforcing material layer, it is poor in steerability. For instance, it is difficult to change the direction of the inner catheter through operating the inner catheter singly.